English

Pronunciation

A parachute is a device used to slow the motion
of an object through an atmosphere by creating drag.

Parachutes are normally used to slow the descent
of a person or object to Earth or another celestial
body within an atmosphere.
Drogue
parachutes are also sometimes used to aid horizontal
deceleration of a vehicle (a fixed-wing
aircraft, or a drag racer),
or to provide stability (tandem free-fall, or space
shuttle after touchdown). The word "parachute" comes from a
French word with a Latin root: "para", meaning "against" or
"counter" in Latin, and "chute", the French word for "fall".
Therefore "parachute" actually means "against the fall". Many
modern parachutes are classified as semi-rigid wings, which are
quite maneuverable, and can facilitate a controlled descent similar
to that of a glider. But
older style parachutes were little more than cloth and sticks. The
design has changed considerably over the years from roughly cut
shapes to aerodynamic ram parachutes. Folding a parachute requires
a high degree of skill, and an improperly folded parachute will not
deploy, which could end up with deadly results.

Parachutes were once made from silk but now they
are almost always constructed from more durable woven nylon fabric,
sometimes coated with silicone to improve performance and
consistency over time. Eventually parachutes need to be replaced as
they deteriorate, as failure to do so could result in loss of
life.

When square (also called ram-air) parachutes were
introduced, manufacturers switched to low-stretch materials like
Dacron or
zero-stretch materials like Spectra, Kevlar, Vectran and
high-modulus aramids.

Early forms

In 9th century Al-Andalus,
Abbas Ibn
Firnas (Armen Firnas) developed a primitive form of parachute.
John H. Lienhard described it in The Engines of Our Ingenuity as "a
huge winglike cloak to break his fall" when he "decided to fly off
a tower in Cordova".

A conical parachute appears for the first time in
the 1470s in an Italian manuscript, slightly preceding Leonardo
da Vinci's conical parachute designs. It was intended as an
escape device to allow people to jump from burning buildings, but
there is no evidence that it was actually ever used. Leonardo da
Vinci sketched a parachute while he was living in Milan around
1480-1483: a pyramid-shaped canopy held open by a square wooden
frame.

The first parachute was invented in 1595 by the Croatian inventor
Faust
Vrančić, who named its invention Homo Volans (Flying
Man).

Twenty years later, he implemented his design and
tested the parachute by jumping from a tower in Venice in 1617. The event was
documented some 30 years after it happened in a book written by
John
Wilkins, the secretary of the Royal
Society in London.

Modern parachutes

The modern parachute was invented in the late
18th century by
Louis-Sébastien Lenormand in France, who made the
first recorded public jump in 1783. Lenormand also sketched it
beforehand. Two years later, Jean-Pierre
Blanchard demonstrated it as a means of safely disembarking
from a hot air
balloon. While Blanchard's first parachute demonstrations were
conducted with a dog as the passenger, he later had the opportunity
to try it himself in 1793 when his hot air balloon ruptured and he
used a parachute to escape.

Subsequent development of the parachute focused
on it becoming more compact. While the early parachutes were made
of linen stretched over a
wooden frame, in the late 1790s, Blanchard began making parachutes
from folded silk, taking
advantage of silk's strength and light weight. In 1797, André
Garnerin made the first jump using such a parachute. Garnerin
also invented the vented parachute, which improved the stability of
the fall. In 1911, Gleb
Kotelnikov invented the first knapsack parachute, later
popularized by Paul
Letteman and Kathchen
Paulus.

The first military use for the parachute was for
use by artillery spotters on tethered observation
balloons in World War
I. These were tempting targets for enemy fighter
aircraft, though difficult to destroy, due to their heavy
antiaircraft
defenses. Because they were difficult to escape from, and dangerous
when on fire due to their hydrogen inflation, observers would
abandon them and descend by parachute as soon as enemy aircraft
were seen. The ground crew would then attempt to retrieve and
deflate the balloon as quickly as possible. No parachutes were
issued to Allied "heavier-thatn-air" aircrew. As a result, a
pilot's only options were to ride his machine into the ground, jump
from several thousand feet, or commit suicide using a
standard-issued revolver (though the last two cases were only
commonly practised by those who did not wish to die by burning). In
the UK, Everard
Calthrop, a railway engineer, and breeder of Arab horses,
invented and marketed through his Aerial Patents Company a "British
Parachute". The German air service, in 1918, became the world's
first to introduce a standard parachute and the only one at the
time. Despite Germany issuing their pilots with parachutes, their
efficiency was relatively poor. As a result, many pilots died
whilst using them, including aces such as Oberleutnant Erich
Lowenhardt (who fell from after being accidentally rammed by a
friendly) and Fritz Rumey (he tested it in 1918, only to have it
fail from a little over 3,000 ft).

Tethered parachutes were initially tried but
caused problems when the aircraft was spinning. In 1919 Leslie Irvin
invented and successfully tested a parachute that the pilot could
deploy when clear of the aircraft. He became the first person to
make a premeditated free-fall parachute jump from an
airplanehttp://www.airborne-sys.com/milestones.htm.

An early brochurehttp://home.earthlink.net/~ralphcooper/pimagz17.htm
of the Irvin Air Chute Company credits William O'Connor 24 August1920 at
McCook
Field near Dayton, Ohio
as the first person to be saved by an Irvin parachute. Another
life-saving jump was made at McCook Field by test pilot Lt. Harold
H. Harris on Oct 201922. Shortly after
Harris' jump two Dayton newspaper reporters suggested the creation
of the Caterpillar
Club for successful parachute jumps from disabled aircraft.
Beginning with Italy in 1927,
several countries experimented with using parachutes to drop
soldiers behind enemy lines, and by World War
II, large airborne
forces were trained and used in surprise attacks. Aircraft crew
were routinely equipped with parachutes for emergencies as
well.

Design

A parachute is made from thin, lightweight
fabric, support tapes and suspension lines. The lines are usually
gathered through cloth loops or metal connector links at the ends
of several strong straps called risers. The risers in turn are
attached to the harness containing the load. As the thin material
inflates it increases drag and in turn slowing down the object it
is carrying. The parachute successfully slows down the object
enough so that it does not break on impact with the ground.

Deployment system

Types of parachutes

Round parachutes

Round parachutes, which are purely drag devices
(that is, unlike the ram-air types, they provide no lift), are
used in military, emergency and cargo applications. These have
large dome-shaped canopies made from a single layer of triangular
cloth gores.
Some skydivers call them "jellyfish 'chutes" because they look like
dome-shaped jellyfish. Modern sports parachutists rarely employ
this style of parachute.

The first round parachutes were simple, flat
circulars, but suffered from instability, so most military round
parachutes are some sort of conical (i.e. cone-shaped) or parabolic
(a flat circular canopy with an extended skirt) US Army
T-10 parachute used for static-line jumps.

Round parachutes are designed to be steerable or
non-steerable. Steerable versions are not as maneuverable as
ram-air parachutes. An example of a steerable round is provided in
the picture of the paratrooper's canopy; it is not ripped or torn
but has a "T-U cut". This kind of cut allows air to escape from the
back of the canopy, providing the parachute with limited forward
speed. This gives the jumpers the ability to steer the parachute
and to face into the wind to slow down the horizontal speed for the
landing. The variables impact the way and the speed that the
parachute falls, because it depends on the speed or the amount of
force in the wind that might change how a parachute falls.

Cruciform (square) parachutes

The unique design characteristics of cruciform
parachutes reduces oscillations and violent turns(swinging back and
forth) during descent. This technology will be used by the US Army
as it replaces its current T-10 parachutes under a program called
ATPS (Advanced
Tactical Parachute System). The ATPS canopy is a
highly modified version of a cross/ cruciform platform and is
square in appearance. The ATPS (T-11) system
will reduce the rate of descent by 30 percent from to . The T-11 is
designed to have an average rate of descent 14% slower than the
T-10D thus resulting in lower landing injury rates for jumpers. The
decline in rate of descent will reduce the impact energy by almost
25% to lessen the potential for injury.

Annular and pull-down apex parachutes

A variation on the round parachute is the pull
down apex parachute—invented by a Frenchman named LeMogne—referred
to as a Para-Commander-type canopy in some circles, after the first
model of the type. It is a round parachute, but with suspension
lines to the canopy apex that applies load there and pulls the apex
closer to the load, distorting the round shape into a somewhat
flattened or lenticular shape.

Often these designs have the fabric removed from
the apex to open a hole through which air can exit, giving the
canopy an annular geometry. They also have decreased horizontal
drag due to their flatter shape, and when combined with rear-facing
vents, can have considerable forward speed around 10 mph (15
km/h).

Ribbon and ring parachutes

Ribbon and ring parachutes have similarities to
annular designs. They are frequently designed to deploy at supersonic speeds. A
conventional parachute would instantly burst upon opening at such
speeds. Ribbon parachutes have a ring-shaped canopy, often with a
large hole in the center to release the pressure. Sometimes the
ring is broken into ribbons connected by ropes to leak air even
more. These large leaks lower the stress on the parachute so it
does not burst or shred when it opens. Ribbon parachutes made of
kevlar are used on
nuclear bombs such as the B61 and B83.

Ram-air parachutes

Most modern parachutes are
self-inflating "ram-air" airfoils known as a parafoil that provide control
of speed and direction similar to paragliders. Paragliders have
much greater lift and range, but parachutes are designed to handle,
spread and mitigate the stresses of deployment at terminal
velocity. All ram-air parafoils have two layers of fabric; top
and bottom, connected by airfoil-shaped fabric ribs to form
"cells." The cells fill with high pressure air from vents that face
forward on the leading edge of the airfoil. The fabric is shaped
and the parachute lines trimmed under load such that the ballooning
fabric inflates into an airfoil shape. This airfoil is sometimes
maintained by use of fabric one-way valves called Airlocks.

Personnel parachutes

Deployment

Reserve parachutes usually have a ripcord deployment system, which
was first designed by Theodore Moscicki, but most modern main
parachutes used by sports parachutists use a form of hand-deployed
pilot
chute. A ripcord system pulls a closing pin (sometimes multiple
pins), which releases a spring-loaded pilot chute, and opens the
container; the pilot chute is then propelled into the air stream by
its spring, then uses the force generated by passing air to extract
a deployment bag containing the parachute canopy, to which it is
attached via a bridle. A hand-deployed pilot chute, once thrown
into the air stream, pulls a closing pin on the pilot chute bridle
to open the container, then the same force extracts the deployment
bag. There are variations on hand-deployed pilot chutes, but the
system described is the more common throw-out system.

Only the hand-deployed pilot chute may be
collapsed automatically after deployment—by a kill line reducing
the in-flight drag of the pilot chute on the main canopy. Reserves,
on the other hand, do not retain their pilot chutes after
deployment. The reserve deployment bag and pilot chute are not
connected to the canopy in a reserve system. This is known as a
free-bag configuration, and the components are often lost during a
reserve deployment.

Occasionally, a pilot chute does not generate
enough force either to pull the pin or to extract the bag. Causes
may be that the pilot chute is caught in the turbulent wake of the
jumper (the "burble"), the closing loop holding the pin is too
tight, or the pilot chute is generating insufficient force. This
effect is known as "pilot chute hesitation," and, if it does not
clear, it can lead to a total malfunction, requiring reserve
deployment.

Paratroopers' main parachutes are usually
deployed by static lines that release the parachute, yet retain the
deployment bag that contains the parachute—without relying on a
pilot chute for deployment. In this configuration the deployment
bag is known as a direct-bag system, in which the deployment is
rapid, consistent, and reliable. This kind of deployment is also
used by student skydivers going through a static line
progression, a kind of student program.

Varieties of personal ram-airs

Personal ram-air parachutes are loosely divided
into two varieties: rectangular or tapered, commonly referred to as
"squares" or "ellipticals" respectively. Medium-performance
canopies (reserve-, BASE-,
canopy formation-, and accuracy-type) are usually rectangular.
High-performance, ram-air parachutes have a slightly tapered shape
to their leading and/or trailing edges when viewed in plan form,
and are known as ellipticals. Sometimes all the taper is in the
leading edge (front), and sometimes in the trailing edge
(tail).

Ellipticals are usually used only by sports
parachutists. Ellipticals often have smaller, more numerous fabric
cells and are shallower in profile. Their canopies can be anywhere
from slightly elliptical to highly elliptical—indicating the amount
of taper in the canopy design, which is often an indicator of the
responsiveness of the canopy to control input for a given wing
loading, and of the level of experience required to pilot the
canopy safely.

The rectangular parachute designs tend to look
like square, inflatable air mattresses with open front ends. They
are generally safer to operate because they are less prone to dive
rapidly with relatively small control inputs, they are usually
flown with lower wing loadings per square foot of area, and they
glide more slowly. They typically have a less-efficient glide
ratio.

Wing loading of parachutes is measured similarly
to that of aircraft: comparing the number of pounds (exit weight)
to square footage of parachute fabric. Typical wing loadings for
students, accuracy competitors, and BASE jumpers are less than one
pound per square foot—often 0.7 pounds per square foot or less.
Most student skydivers fly with wing loadings below one pound per
square foot. Most sport jumpers fly with wing loadings between 1.0
and 1.4 pounds per square foot, but many interested in performance
landings exceed this wing loading. Professional Canopy pilots
compete at wing loadings of 2 to 2.6 pounds per square foot. While
ram-air parachutes with wing loadings higher than four pounds per
square foot have been landed, this is strictly the realm of
professional test jumpers.

Smaller parachutes tend to fly faster for the
same load, and ellipticals respond faster to control input.
Therefore, small, elliptical designs are often chosen by
experienced canopy pilots for the thrilling flying they provide.
Flying a fast elliptical requires much more skill and experience.
Fast ellipticals are also considerably more dangerous to land. With
high-performance elliptical canopies, nuisance malfunctions can be
much more serious than with a square design, and may quickly
escalate into emergencies. Flying highly loaded, elliptical
canopies is a major contributing factor in many skydiving
accidents, although advanced training programs are helping to
reduce this danger.

High-speed, cross-braced parachutes such as the
Velocity, VX, XAOS and Sensei have given birth to a new branch of
sport parachuting called "swooping." A race course is set up in the
landing area for expert pilots to measure the distance they are
able to fly past the tall entry gate. Current world records exceed
.

Aspect ratio is another way to measure ram-air
parachutes. Aspect ratios of parachutes are measured the same way
as aircraft wings, by comparing span with chord. Low aspect ratio
parachutes (i.e. span 1.8 times the chord) are now limited to
precision landing competitions. Popular precision landing
parachutes include Jalbert (now NAA) Para-Foils and John Eiff's
series of Challenger Classics. While low aspect ratio parachutes
tend to be extremely stable—with gentle stall characteristics—they
suffer from steep glide ratios and small "sweet spots" for timing
the landing flare.

Medium aspect ratio (i.e. 2.1) parachutes are
widely used for reserves, BASE, and canopy formation competition
because of their predictable opening characteristics. Most medium
aspect ratio parachutes have seven cells.

High aspect ratio parachutes have the flattest
glide and the largest "sweet spots" (for timing the landing flare)
but the least predictable openings. An aspect ratio of 2.7 is about
the upper limit for parachutes. High aspect ratio canopies
typically have nine or more cells. All reserve ram-air parachutes
are of the square variety, because of the greater reliability, and
the less-demanding handling characteristics.

General characteristics of ram-airs

Main parachutes used by skydivers today are
designed to open softly. Overly rapid deployment was an early
problem with ram-air designs. The primary innovation that slows the
deployment of a ram-air canopy is the slider;
a small rectangular piece of fabric with a grommet near each corner. Four
collections of lines go through the grommets to the risers. During
deployment, the slider slides down from the canopy to just above
the risers. The slider is slowed by air resistance as it descends
and reduces the rate at which the lines can spread. This reduces
the speed at which the canopy can open and inflate.

At the same time, the overall design of a
parachute still has a significant influence on the deployment
speed. Modern sport parachutes' deployment speeds vary
considerably. Most modern parachutes open comfortably, but
individual skydivers may prefer harsher deployment.

The deployment process is inherently chaotic.
Rapid deployments can still occur even with well-behaved canopies.
On rare occasions deployment can even be so rapid that the jumper
suffers bruising, injury, or death.

For example, one method of reducing the
air-resistance of a reserves slider is to make it of open-mesh
fabric.

Safety

A parachute is carefully folded, or "packed" to
ensure that it will open reliably. If a parachute is not packed
properly it can result in death because the main parachute might
fail to deploy correctly or fully. In the U.S. and many developed
countries, emergency and reserve parachutes are packed by "riggers"
who must be trained and certified according to legal standards.
Sport skydivers are always trained to pack their own primary "main"
parachutes.

Parachutes can malfunction in several ways.
Malfunctions can range from minor problems that can be corrected
in-flight and still be landed, to catastrophic malfunctions that
require the main parachute to be cut away using a modern 3-ring
release system, and the reserve be deployed. Most skydivers
also equip themselves with small barometric computers (known as an
AAD or
Automatic Activation Device like Cypres, FXC or
Vigil) that will automatically activate the reserve parachute if
the skydiver himself has not deployed a parachute to reduce his
rate of descent by a preset altitude.

Exact numbers are difficult to estimate, but
approximately one in a thousand sports main parachute openings
malfunction, and must be cut away, although some skydivers have
many hundreds of jumps and never cut away. Reserve parachutes are
packed and deployed differently. They are also designed more
conservatively, and are built and tested to more exacting
standards, making them more reliable than main parachutes. However,
the primary safety advantage of a reserve chute comes from the
probability of an
unlikely main malfunction being multiplied by the even less likely
probability of a reserve malfunction. This yields an even smaller
probability of a double malfunction, although the possibility of a
main malfunction that cannot be cut away causing a reserve
malfunction is a very real risk. In the U.S., the average fatality
rate is considered to be about 1 in 80,000 jumps. Most injuries and
fatalities in sport skydiving occur under a fully functional main
parachute because the skydiver made an error in judgment while
flying the canopy—resulting in high-speed impact with the ground,
impact with a hazard on the ground that might otherwise have been
avoided, or collision with another skydiver under canopy.

Parachute malfunctions

Below are listed malfunctions
specific to round-parachutes. For malfunctions specific to square
parachutes, see Malfunction
(parachuting).

A "cigarette roll" occurs when a parachute
deploys fully from the bag but fails to open. The parachute then
appears as a vertical column of cloth (in the general shape of a
cigarette), providing the jumper with very little drag. It is
caused when one skirt of the canopy, instead of expanding outward,
is blown against the opposite skirt. The column of nylon fabric,
buffeted by the wind, rapidly heats from the friction of the nylon
rubbing against nylon and can melt the fabric and fuse it together,
preventing any hope of the canopy opening.

An "inversion" occurs when one skirt of the
canopy blows between the suspension lines on the opposite side of
the parachute and then catches air. That portion then forms a
secondary lobe with the canopy inverted. The secondary lobe grows
until the canopy turns completely inside out.